[ASD] [VSD] [PDA] [Coarctation] [Tetralogy of Fallot] [Pulmonary Atresia] [Tricuspid Atresia] [HLHS] [Transposition] [DORV] [TAPVC] [AV Canal] [Pulmonary Stenosis] [Truncus Arteriosus] [Ebstein's Anomaly] [Coronary Anomalies] [Single Ventricle]
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There are many such situations.
If, for instance, the pulmonary artery branches are NOT AT ALL developed (Pulmonary Atresia), a one-stage total correction operation is obviously impossible. For then, where would blood from the right ventricle go ?
Somewhat similar is the condition where the outflow tract of the right ventricle is VERY narrow at any portion - at the valve, or above it, or in one of the branches. Here, even with repair and widening of the narrowed area, significant block to blood flow will persist. If a one-stage operation is performed, then all the blood from the right ventricle would be FORCED to travel through the repaired, yet narrow outflow tract. What happens then ? The right ventricle has to work harder to pump blood through a narrow passage - it is like packing all your clothes into a very small suitcase, you have to push harder to get it all in ! And the right ventricle cannot do this forever. It gets tired, and "fails". If a palliative operation is done first, this problem can be avoided.
Then again, there are some babies who are too small. They would not be able to tolerate a major operation like a total correction straight away. Or there may be many other birth defects (multiple VSDs, abnormal coronary arteries) associated with ToF. The presence of such defects would greatly increase the risk of a direct total correction.
The only significant problem in ToF needing palliation is the REDUCED blood flow into the lungs. This results in less oxygen delivered to the rest of the body.
The operations designed to increase blood flow into the lungs are called SYSTEMIC - PULMONARY SHUNTS. These are connections between the aorta or one of its branches (the "systemic" arteries) and the pulmonary artery. The principle underlying these shunts is that a portion of blood flow from the arteries will be directed across the shunt into the pulmonary artery and its branches. This has two effects.
This shunt was the first of its kind, and revolutionised the treatment of "blue-baby" disease. Dr.Helen B.Taussig was a famous cardiologist, who studied heart disease in children in great detail. She thought of the idea of diverting blood from the SUBCLAVIAN ARTERY, which is a branch of the aorta, to the pulmonary artery. (The subclavian artery is so named because it lies under - "sub" - the collar bone or clavicle - "clavian") . By improving the amount of lung blood flow, and increasing the oxygen content, it would relieve the cyanosis - or bluish discoloration.
In Dr.Alfred Blalock, she found a surgeon both skilled enough and daring enough to attempt this procedure on sick children. After practising many times on experimental animals, Dr.Blalock performed the first "SHUNT" operation on September 23rd, 1944 at Johns Hopkins Hospital, Maryland, USA.
The results were dramatic. At the end of the operation, when the clamps blocking the shunt were released, the blue color of the child disappeared. Instead, the child turned a healthy pink - and the operating room personnel burst into spontaneous applause ! As an interesting sidelight, the famous heart surgeon, Dr.Denton Cooley, was the intern assisting at this history-making operation, and said it was one of the things that made him select heart surgery as his specialty !
Ever since, the Blalock-Taussig shunt, or its MODIFIED version, have been used in palliation of thousands of children with ToF, with great success.
Through an opening on one side of the chest, the surgeon has to first identify and free the pulmonary artery and the subclavian branch of the aorta. He or she then applies clamps on both vessels, to prevent bleeding which may obscure vision during the creation of the shunt. The subclavian artery is divided, turned down and then stitched to an opening in the side of the pulmonary artery using fine hair-like thread made of Prolene.
Although widely performed before, this shunt has a few problems. The isolation and division of the subclavian artery is a time consuming and difficult procedure. Also, it carries a small risk of damaging nerves that supply the hand and arm muscles, and blood supply to the upper limb.
In the modified version, which is most commonly performed now, the subclavian artery is not divided. Instead, an artificial tube made of material like PTFE (a special polymer of ethylene) is used to make the connection. After applying clamps as usual, an opening is made in the side of the subclavian artery to which one end of the PTFE tube is stitched using fine thread. The other end of the PTFE tube is then brought down. It is stitched to another small opening in the side of the pulmonary artery. In this way, the same effect is achieved, without interrupting either artery and with lesser risk.
The effects of a Blalock-Taussig shunt are immediate, and usually last long. The severity of cyanosis ("blueness") is reduced. However, it is only a temporary measure. It aims to improve oxygen supply and promote growth of the pulmonary artery branches. Once these aims are achieved, a total correction operation can be performed safely.
A Blalock-Taussig shunt is a reasonably safe procedure, with a risk of death below 1%. Complications are rare and include:
Instead of choosing the subclavian artery, other branches of the aorta, or even the aorta itself may be chosen to provide more blood flow into the pulmonary artery.
In the POTTS shunt, a direct connection is made between the lower part of the aorta in the left side of the chest and the left branch of the pulmonary artery. This operation used to be frequently performed in older days, but has more or less been given up now. This is because of certain drawbacks, both in its function, and in the difficulty of later closing it during the time of total correction operation.
In the WATERSTON - COOLEY shunt, a direct connection is made between the back of the aorta and the right branch of the pulmonary artery. Though still popular in some hospitals, it is a little more difficult operation to perform perfectly.
In the DAVIDSON shunt, a short tube of PTFE is used to create a shunt between the aorta and the pulmonary artery through an opening in the middle of the chest.
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